Method of testing open wells



Dec. 6, 1932'. G, H, ENNls 1,889,889

METHOD OF TESTING OPEN WELLS Filed Feb. 3. 1930 2 Sheets-Sheet l vELECTROLYTE [NI/ENTaR' ear e H [121219 A TragggEX Dec.'6, 1932. a. H.ENNIS ,3

' METHOD OFTESTING OPEN WELLS File d Feb. 3. 1930 2 Sheets-Sheet 2 sz'725/5. $514. I

Patented Dec. 6, 1932 YEUNITED STATES" PATENT. OFFICE:

Gannon H. ENNIS, or LONG amen, cannroimm, ASSIGNOR or ONE-HALF 'roROBERT v. 1

JUNE, OF LONG BEACH, CALIFORNIA rmrnon or trnsrineoran warms lApplication filed February 3, 1930. Serial No. 425,521.

My invention relates to the testing of a well for determining. the pointat which water enters the well, and it further relatesto an improvedelectrolytefor use in such tests.

i In the drilling of an oil well it invariably occurs that water bearingstrata are penetrated before the oil sands are reached. The

water bearing strata must be sealed from the well; otherwise,the waterwill run thereinto, forming an emulsion, and in some'instances reducingthe oil yield of the well tothe extent that the operation of the well isimpractical.

According to present practice, the well is drilled and .various' casingsare set in place. If it is found that water is leaking into the well,the point of leakage must be found and the water bearing strata mustbesealed off. This sealing operation is usually ''accomplished byextending a casing down to a shale or rock stratum below the waterbearing strata and cementing the casing thereto. The last casing usuallyinstalled in a well is known as the oil 'string- The lower end of theoil stringis extended into the oilsands and is perforated to allow theoil'to enter. a

The upper end of the oil is above the surface of the ground and isconnected to piping for conveying away the oil. Some-* times waterbearing strata are located adj acent the oil sands,and a portion of theperforated pipe passes therethrough, this allowing the ingress of waterinto the well. When this condition exists, thewater bearing-strata mustbe found and cemented from the well.

The foregoing outlines the procedure of installing casing andcementingcasing in a well when water leakages are" encountered.

. There are processes at-present for locating the leakage of water intothe well after the caslng strings have been set, and such a process isdisclosed in my patent entitled Method and apparatus for determining thelocation of water strata in wells, No. 1,786,196, issued Dec. 23, 1930.Y

During the" period of drilling and setting the casing, the well is keptfull of rotary mud, which serves a number of purposes, such as holdingthe formations in place, preventing cave-ins and preventing prematureflows of and the rotarymud removed from the well,

so that the hydrostatic head is reduced suf ficiently' so that thepressure against the formations is insufiicient to restrain an inwardflow. At this time if there are any I openings in or around the casingadjacent to or in communication with the water strata, the'water willstart to leak into the well.

It will therefore be seen that ordinarily the operator of the well hasno way 0f.kn0wing whether'or not there will be water leakages into thewell until after all the casings have been installed and the rotar mudremoved from the well so that the hy rostatic head is reduced. Manythousands of dollars are sometimes spentin installing a casingin a well,and then when the rotary mud is removed, it is found that water stillleaks into the well.

It is the purpose of my present invention 1 to provide a method wherebthe well may be tested for water leakages efore all of, the

casings have been setand' before the rotary mud has been removed, thusenabling the water leakages to be located and then sealed from the wellby cementing or by the installation of the next casing. My inventionfurther makes it possible to test a well for water leakages before anyflow of oil has been started. I

The preferred method of my invention includes the placing of anelectrolyte in the well near the leakagepoint, if it can be estimatedfrom the log of the well, or throughout the entire wellif nece ssary,moving a pair of electrodes through the electrolyte, the electrodescooperating with the surrounding portion of the electrolyte to providetavoltaic'cell, and measuring the potential difi'erencebetween theelectrodes as they are moved through different positions in the well. Aswater seeps into the well, the electrolyte is weakened, which willchange the potential difference between the'electrodes and thus indicateto the operator whereat the leakage occurs. In performing my method inanopen hole.

portion is unprotected by easing, the rotary imud 1S maintained in thehole for a number of reasons, as pointed out above. In order to test thewell to locate the water strata, an electrolyte must be introduced intothe well.

This electrolyte which is to be used must possess all of the qualitiesof the rotary mud, such as pointed out heretofore, as well as itselectrochemical qualities. It is further neeessar that the electrolytehave qualitieswhic prevent it from stratifying and prevent it from beingdriven into the formations by the hydrostatic head in the well.

My invention provides an electrolyte which has the essential qualitiesas specified above,

which renders the method of testing in an open hole a success, bypreserving the condition of the well during the testing.

I will now describe my invention in detail,

and during the course of the following description reference will hehadto the accompanying drawings in, which:

Fig. 1 is a view illustrating a drilled well which is ready to be testedby my invention. Fig. 2 is a view similar to Fig.1 showing the testingapparatus in the well, which testing apparatus is of a type capable ofperforming my invention. a

Fig. 3 is an enlarged sectional view showing a portion of the well withthe electrolyte of my invention therein showing the manner in which thewater leakage occurs to-dilute the electrolyte.

Fig. 4 is a section through the electrode carrier used in performing myinvention. 4

Fig. 5 is a section'taken on the line 55 of Fig. 4. v

Fig. 6 is a chart showing a series of tests actually made on a well ofthe Associated Oil Company in southern California.

'Referring particularly to Fig. 1, the numeral 11 represents the well.According to customary methods well casings 12 and 13 are installed inthe upper end of the well and cemented in place, as indicated at 14. Thenumerals 15'and 16 represent shale or rock formation. The numeral 17represents a water bearing formation, and the numeral 18 represents theoil sand. Fig. 1 shows the well after drilling operations have ceasedand before the final casing is set. The well at this time is filled withrotary mud 19 in order that the lower open portion 20 of the well willreceive the necessary reinforcement to prevent cave-ins, and'in orderthat there will be no flow of oil prior to the installation of the finalcasing and the necessary preparation at the surface of the well.

If any of the rotary mud is removed from the well at this time, thehydrostatic head mud, such as holding the preventing bridging,lubricating the walls will be reduced, and thewalls of the open hole maycave 1n. It is the usual practice to install the various casings in thewell immediately after the drilling operations have been completed andto then-remove the r0 tary mud from the well. If the siibterranean Thefirst step in the process of my inven tion is performed when the well isin the condition shown in Fig. 1;thatis to say, drilling operations havebeen completed and the well is full of rotary mud, as shown.

The'first step consists in introducing an electrolyte into the well. Theelectrolyte, which is indicated by the numeral 21 in Figs. 2 and 3,maybe introduced at certain portions of the well so that the well may betested by stages, or the entire well may be filled with thiselectrolyte.

The electrolyte which is used in the process must serve all of thepurposes ofrotary of the well, preventing cave-ins, controlling thepressures, controlling the water, controlling the oil, controlling thegas, and holding angle formations in tion to this, the electro te musthave its electrochemical characteristics and function as a part of avoltaic cell. The electrolyte which I use includes a number ofsubstances to endow it with the necessary characteristics.

For the'electrochemical qualities .1 may use a solution of ammoniumchloride, which isstrongly ionizable, or an equivalent ionizablemateriag which will retain its electrochemical qualities in the presenceof the other substances the electrolyte.

I may also use as an electrochemical material a solution which includesammonium sulfate, sodium sulfate, and a colloidal material in a solutionwhich is acid, with sulfuric acid and chromic acid. The colloidalmaterial which I prefer to use is alcohol fermentation product of wastemolasses after the removal of the alcohol therefrom. It is knownteehnicallyas slop. This electrochemically active solution may be madeas follows:

#1 Slop solution ormation in place,

lace; and in addiwhich comprise a part of cold water.

\ weight) 66 Be. sulfuric acid.

#2 Ammonium sulfate solution f tilizer grade ammonia) in 60 gallons of[#3 Sodium biahromate solution 3% parts ("by weight) water, 3 parts byweight) sodium bichromate, 1 part 'Mia-ing Take 90 gallons ammoniumvsulfateof A solution. Make up 150 gallons of sowell by patented dosedistributor.

amount of solution used is 1 gallon of sumv tionapproximately to each 48gallons of terial, or colloidal mineral, which is dium bichromate or Bsolution. Mix 4 parts by volume of A solution and 6 parts of B solution,making 250 gallons of chemical solution to be distributed in fluidcontents1 lof e liquid in the well. 7

To endow the electrolyte with the necessary weight qualities which areessential to'the electrolyte in order that it may support the walls ofthe holeand holdback the flow of oil, a heavy mineral in finely dividedform is included in the electrolyte. As a weight material I prefer touse barium sulfate, BaSO and in some instances I add to'the bariumsulfate a glutinous or colloidal mineral, such as bentonite clay orother colloidal clays. The purpose of the bentonite clay, or thecolloidal ineral, is to prevent the electrolyte from ing driven by thehydrostatic head into the formation and to prevent stratis -fi cationof-the different substances which compose the electrolyte.

' The proportions of the electrochemical material and the weightmaterial, which is preferably barium sulfate,'and the glutinous m:-

' erably bentonite clay, is used in accor ance withthe requirements ofthe well. In some wells the formation is such that the specific gravityof. the electrolyte may be lower than in other instances, and likewisein some wells it is desirable to use more or less colloidal mineralingredients with the tendency of the electrolyte to penetrate thestrata. In some instances the colloidal material may beeliminated, but Ihavefound that the most satisfactory electrolyte is formed when at leasta small percentage of colloidal mineral is used, due to the fact thatthe colloid'al'min- ,eral acts as a suspender and prevents the differentsubstances of the electrolyte from stratifying. j

As an example of the proportions which I may use toform the electrolyteof my in- 1 vention, I give the following formula. It

hours.- Siphon 51! 10 Dissolve 300# of ammonium sulfate (fershould beunderstood, however, that this formula is illustrative only, and I donot intend to limit myself to the proportions stated.

Per cent The electrolyte may be introduced into the well. in variousmanners. One way of introducing the electrolyte is to use thedistributor disclosed in my patent for dosedistributor,

No. 1,725,979, patented Au ust' 27, 1929.

Another met lyte' is to extend into the well 11 a pipe or tube 25 whichis connected to a pump 26 which draws the electrolyte from a source ofsupply. The electrolyte is pumped through the pipe 25 into the well, thelower end of the pipe extending to the lower end of the well or to i apoint where the electrolyte is to be introduced. By this means theentire well or a portion of the well may be filled with electrolyte.If'desired, it is practical to test the well in sections, fillingdifferent portions of the well with electrolyte, so that it is notnecessary to use a large amount of the electrolyte. In Fig. 2-theelectrolyte 21 is shown as placed between the lower andupper bodies ofrotary mud 30 and 31 respectively. It is sometimes possible to locatethe ingress of water by the use of a charge of electrolyte whichisproperly placed according to indications given to the driller duringthe drilling operation. a

In the step of introducing the electrolyte into the well it isabsolutely essential to maintain a hydrostatic head-which is sufiicientto prevent cave-insand to prevent a premature flow of oil. The twomethods outlined are iatisfactory ones for introducing the electro--yte.

0d of intro ucing the electro- Thenext stepin the process isto make atest of the well to determine the-uniformity of the electrolyte whichhas been introduced.

This is accomplished byusing the testing device shown in Figs, 2, 4, and5.

The testing device consists of a frame '32 having a guide means 33 atthe lower end thereof and having a cable 34 attached to the upper endthereof. Supported in theshell 32 is an insulation block 35 having acentral opening 36, which insulation block 35 supports a. pair ofrelatively spaced electrodes 37 and 38.

The electrodes 37 and 38 must be made of such material aswill cooperatewith the electrolyte to form avoltaic cell.. It is well known in the artwhat metals may be used'for this purpose. In my device, I find itelectrical conductors 40 and 41 which may be extended to the surface ofthe ound through the cable 34. The cable 34 extends over a guide sheave42 and may be wound on a suitable drum 43. The conductors 40 and 41 arejoined to rings 44 and 45 which are engaged by brushes 46 and 47respectively. The

ushes are included in conductors 49 which are joined to a millivoltmeter50. The testing device, which will be generally indicated by the numeral51, is lowered by means of the cable 34 through the electrolyte 21.When- I passing through the electrolyte 21, themillivolemeter 50 shouldgive a constant reading and usually 'ves a reading of about 200 ointswhich is about 10 millivolts. If it is ound that the electrolyte isuniform, the next step in the process is conducted. If a nonuniformreading is obtained, a redistribution of the electrolyte must beperformed.

' The next step in theprocess is to cause the flpw of fluid into thewell from the surroundin formation. This is preferably accompllshed byreducing the hydrostatic head in the well. A bailer may be extended intothe upper end of the well, and a relatively small amount of the rotarymud or of the electrolyte removed from the top of the well. When thehydrostatic head is thus reduced, the pressure of the electrolytetending to hold the fluid -in the formation is reduced and will permitan inflow into the well. As shown best in Fig. 3, the electrolyteadjacent to the water bearing formation will be diluted or' weakened, asindicated at 60, by the inflow of water. u

' The testing apparatus is again moved through the electrolyte in themanner just described. 'Where the electrolyte is undiluted, thereadingwill be the same as prior to the step just described of causing fluid toflow into the well from the surrounding formation. Where the fluid hasflowed into the well, however, the strength of the electrolyte will bereduced and the millivoltmeter will show a lower reading. Another way ofexpressing the same function is that when the two electrodes 37 and 38are in the unadulterated electrolyte, the potential difference willremain constant. When the. electrodes move to that portion of theelectrolyte which has been diuted and Where the electrochemical actionhas been reduced, the potentialdifference between the electrodes will bereduced in a certain proportion.

It is usually desirable to retest a well two or three times byperforming the two preceding steps. In other words, the hydrostatic headis reduced to permit the flow of fluid into the well, and the testis'made; then the hydrostatic head is again reduced to cause a flow ofadditional Water into the well.

. In Fig. 6, the test chart shows four tests was made before thehydrostatic head had been reduced. Test No. 2 was made after the hdrostatic head had been reduced once. Test 0. 3 was made after thehydrostatic head had been reduced. twice, and Test No. 4 was made afterthe hydrostatic head had been reduced a third time. At the upper end ofthe separate readings, the numerals 20, 40, 60, etc. to 200, representcalibrations on the millivoltmeters. The cross-hatched portions of thechart represent the reading given by the millivoltmeters at the variousdepths mdicated on the left side. of Fig. 6. In Test No. 2 it is shownthat the electrolyte was diluted at a depth of 8250 to 8270 feet. TestNo. 3 shows that the electrolyte H at 8260 to 827 0 feet'was diluted themost. As

more water had entered the well, however,

the water spread slightly so that the dilution ofthe electrolytecommenced at 8190 feet. In Test No. 4, a complete bridgin of,

the water occurred at 8270 feet. The ilution of the electrolyte extendedup to 8040 feet. The chart shown in Fig. 6 has been .made from readingstaken during the test of a well in southern California.

' The step just described in connection with Fig. 6 completes the"method of my invention. The location of the water entry has been found,and, as indicated by the chart referred to, the water in that particularwell entered at a level of 8250 to 8270 feet. The next activity in thewell is to seal the water bearing stratum from the well. This may bedone by extending a casin' downward to the shale or rock stratum, suc as16, located below .the water bearing formation 17. The casing is thencemented in place, which completely, seals the water from the well. somecases the leakage ma forming a cement plug in til drilling through it.

e well and then In be arrested by The operator will then install the oilstring and prepare the equipment at the surface of'the ground foraccommodating the oil. The rotary mud is then removed. If the well is. aflowing well, the oil will commence to flow. If not, pumping apparatusmust be installed and the oil pumped to the surface of the ground. '1

My invention is not limited to use in o n hole's but may be used afterall casing his been set and either before or after the rotary mud hasbeen removed. I claim as my invention:

1. A method of testing a well to find water leakages, prior to theremoval of rotary mud from the well, said method comprising: placing abody of electrolyte in said well between layers of rotary mud; bailingrotary mud from the upper end of the well to allow an ingress of water;and electrochemically testing said electrolyte to determine whether ornot it has been diluted.

65 which 'were made on a well. Test No. 1 2. A method of testing a wellto'find water leakages, prior to the removal of rotary mud from thewell, said method comprising: incorporating a weight material in anelectrolyte; placing a body of said electrolyte in said well betweenlayers of rotary mud; bailing rotary mud from the upper end of theWell-to allow an ingress of water and electrochemically testing saidelectrolyte to determine whether or not it has been diluted.

3. A method of testing a wellto find water leakages, prior to theremoval of rotary'nuld ,from the well, said method comprising: in-

, leakages, prior to the removal of rotary mud from the well, saidmethod comprising: iu-

corporating a weight material and a glutinous material in an electrolyteplacing a body of said electrolyte in said well between layers of rotarymud; bail-ing rotary mud from the upper end of the well to allow aningress of water; and electrochemically testing said electrolyte todetermine whether or not it has been diluted:

5. A method of testing a well to find water leakages, prior to theremoval of rotary mud from the well, said method con'iprising:incorporating a weight material and a colloidal clay in an electrolyte;placing a body of said electrolyte in said well between layers of rotarymud; bailing rotarymud from the upper end of the well to allow aningress of water; and electrochemically testing said from the well, saidmethod comprising: forming an electrolyte of substantially the sameglutinous characteristics as said rotary mud; placing a body of saidelectrolyte in said well between layers of rotary mud; bailing rotarymud from the upper end of the well to allow an ingress of water; andelectrochemically testing said electrolyte to determine whether or notit has been diluted. 9. A method of testing a well filled with a liquid,said method comprising: incorporating a weight material in anelectrolyte to make it of substantially the same specific gravity assaid liquid; placing said electrolyte in said well between two layers ofliquid; bailing said liquid from said well, and electrochemicallytesting said electrolyte- In testimony whereof, I have hereunto set myhand at Los Angeles, California, this 28th day of January, 1930.

Y GEORGE H; ENNIS.

electrolyte to determine whether or not it has been iluted. I I

6. A method of testing a well to find water leakages, prior'to theremoval of rotary mud from the well, said method comprising: a

forming an electrolyte of substantially the samedensity as sai rotarymud, placing a body of said electrolyte in said well between layers ofsaid rotary mud; bailing rotary mud from the upper end of the well toallow an ingress of water; and electrochemically testing saidelectrolyte to determine whether or not it has been diluted.

'7. A method of testing a well to find water leakages, prior to theremoval of rotary mud from the well, said method comprising: forming'anelectrolyte of substantially the same viscosity as rotary mud; placing abody of said electrolyte in said well between layers of rotarymudibailing rotary mud from the upper end 'of the well to allow aningress of water; and electrochemically testing said electrolyte todotern'line whether or not it.

has been dilutdd.

8. A method of testing a well to find water

